Recent smartphone security enhancements in the APPLE iOS® and the Android® operating systems result in an unacceptable uncertainty in the sensor and smartphone synchronization methods disclosed in the above referenced Provisional Applications 62/178,034 and 62/282,571 resulting in a very large, over 400 ms, potential error in the calculated run time. The present invention discloses a method whereby the actual run time is derived to reduce the residual synchronization error to +/−8 ms to thereby stay within an acceptable +/−10 ms error limit to avoid the new security induced errors. A one-time calibration routine is used to characterize the relative time drift between the crystals of the smartphone's time base and that of the motion sensor time base. Once calibrated, the relative time base drift error is fully characterized and can be used to remove the error in all future run time calculations. Once calibrated, the long term variation of the crystals, in terms of temperature and aging, is effectively negligible and can be considered constant over the life of the motion sensor.
Often an athlete in training is clocked for the time taken to cover a premeasured distance which entails a starting signal to start timing of the event and an end signal to stop timing the event. The starting signal may be an audible sound or series of sounds, such as by way of examples, a whistle, beep, siren or shot sound. For an end signal, a trainer may use a stop clock or a camera with a time stamp to determine the end of the event. It is an object of the present invention to provide a method and apparatus for training by which the athlete no longer needs a second person to clock the time taken to cover the predetermined distance thus providing maximum scheduling flexibility for the training time.